118 



KNOWLEDGE. 



[May, 1901. 



these colours fade, the flagella become increasingly fine until at 

 last they are no longer visible. 



This is a subject in ■which, to the ordinary mieroscopist, few 

 opportunities are afforded of making experiments, but a good 

 service would be rendered if some really definite and permanent 

 process, based on an understood system, could be formulated. 



Tub RiiYAi. jMiCROSCOPifAi. Sociktv. — This Society is well 

 known by name to microscopists in all parts of the world, but 

 comparatively few are aware of the advantages that are 

 associated with the Fellowship of the Society. It has ever 

 been the foremost to recognise and to encourage progi'ess and 

 improvements in matters microscopical, and in consequence of 

 the efforts of the various members, that progress and those 

 improvements have been in many instances directly attributable 

 to the Society's work. 



The advantages directly derived by a Fellow of this Society 

 are : — 



He is supplied with a journal bi-monthly, published at 6s. 

 . per number, which is the most exhaustive publication 

 on microsco|iical technique that is issued. 

 The rooms of the Society, together with a very fine library, 

 cabinets of beautiful objects, and microscopes for 

 making examinations, are open and available for use 

 throughout the year with a .short interval only in the 

 middle of August. 

 The meetings of the Society are held at 20, Hanover Square, 

 on the third Wednesday in each month, upon which 

 occasion exhibitions of specimens and new apparatus 

 are made, papers are read, and opportunities afforded 

 for conversing with experts on various subjects. 

 The inclusive subscription i)er annum is £2 2s., but those 

 living permanently^abroad are entitled to become Fellows and 

 receive the journals for a subscription of ?>ls. Od. per annum. 



The Secretary would be glad to give further information 

 concerning this Society, and a ticket for admission to any of the 

 meetings, on application to him at the Society's Rooms, 20, 



Hanover Square, W. 



►.*.< 



NOTES AND QUERIES. 



11'. E., Ci-eiae. — The question naturally arises whether the 

 microscope you require is to be used exclusively for petrological 

 work, or do you wish it to be available for ordinary observations. 

 If the former, the " Dick " microscope, by Messrs. Swift & 

 Sons, is exceedingly efficient and comprehensive ; if the latter, 

 Messrs. R. & .1. Beck, and W. Watson & Son.s, offer .some well- 

 designed models. Of Continental manufacturers, R. Feuss, 

 of Steglitz, is the one man whose petrological instruments have 

 distinct advantages. It would be advisable for you to get 

 catalogues from these different people, and ascertain by that 

 means what featui'es appeared to be of special importance for 

 your work, and if then I could give you any further advice 

 or assistance I would gladly do so. 



The liec. (j. C. J. — Your trouble arises from using cedar- 

 wood oil for clearing ; you will find the following procedure 

 answer well : Dehydrate in absolute alcohol, clear in chloroform, 

 and transfer to paraffiu. 



ir. //. C. — No further discussion has taken place on the 

 Abbe diffraction theory, so far as I am aware. Diatoms 

 can be found almost everywhere ; the smallest ditch or pool, 

 provided the water is not stagnant, will yield material. The 

 specimen of which you send a sketch is probably a form of 

 Navicula, but it is impossible to tell without actually examin- 

 ing the specimen. You are eligible for membership of the 

 Quekett Club, and either the secretary, or the optical house 

 from which you obtained your microscope, would put you in 

 the way of being nominated. 



Mr. Cooper AVebb, F.C.S., has sent me a photo-micrograph of 

 the Cat Louse — Tr/clioilectex siihroittmliis. He states that this 

 was " discovered by Mr. Parkes on some English cats at 

 Eastbourne in February last, and may be of interest to some of 

 the entomological readers of Knowi.eiice, for according to such 

 eminent authorities as Denny, Andrew Murray, and, I think, 

 Burmeister, this parasite had not hitlierto been discovered in 

 the country.'' If any microscopists arc interested in the above, 

 I shall be pleased to put them in communication with my 

 correspondent. 



J. C. Webb. — I am communicating your offer to the society 

 referred to. 



ir. P. Uinnilton, — I am very much obliged for the red rain 

 (lust, and will mount some and give the result in next month's 

 number. 



A'. //. .lA. — " Could you kindly inform me whether there is 

 any book published that treats fully on the microscopical 

 anatomy of insects, as I am anxious to take u]) that particular 

 branch of research V " Can any reader offer a suggestion '? 



li. M. — " I have for some time made a s|)ecial study of 

 Desmidiaceas, especially Closterium, and should be glad to 

 know of some book which treated of the life-history of 

 Desmidiacea3. In particular I am anxious to discover the cause 

 for swarms of Closterium, which in spring time come up from 

 the mud to the surface of the water, quantities of ten to 

 twenty being connected by a thin mucous filament.'' 



Communications and enqu/rien mi Microscopical matters are 

 cordially invited, and shoidd be addressed to M. I. CROSS, 

 Knowledge Office, 326, High Eolhorn, W.C. 



NOTES ON COMETS AND METEORS. 



By W. F. Denning, f.r.a.s. 



The frequency with which periodical comets escape detection is 

 perhaps not a httle remarkable. Recently the comets of Finlay, 

 Barnard (188-t), E. Swift (1894, lY.), and firorsen have been sought 

 for in vain. It is true that the conditions vary greatly at different 

 returns, and are not often reaDy favourable to the detection of 

 these bodies. And in regard to those comets which have only been 

 observed at a single apparition the positions are seldom accurately 

 known. The visibility of these objects is also subject to considerable 

 fluctuations, due to some inherent physical causes which are not 

 well understood and cannot be sufficiently allowed for. Holmes's 

 comet, wliich was, fortunately, detected at its first periodical 

 return in 1899, was exceedingly faint then, though its conspicuous 

 appearance in the autunm of 1892 justified the inference! that it 

 would be pretty bright. The failure in re-detecting some of these 

 interesting bodies is to be regretted, since it is most desirable to 

 obtain observations at multiple returns in order to determine the 

 orbit elements with accuracy. Certain comets are only visible at 

 alternate returns, others at one out of several returns. The 

 numerous failures to pick up these objects cannot be ascribed to 

 negligence on the part of those having the command of large 

 instruments, for the latter have often been successfully employed 

 in work of this kind. Perhaps the effort has not always been 

 adequate to the occasion, and it is to be hoped that some more 

 systematic method will be adopted in future. If combined action 

 were arranged between the possessors of really powerful telescopes 

 every expected comet might be effectively looked for, whereas under 

 present circumstances some comets receive a good deal of attention, 

 while others have very little, and are enabled to elude recovery. 



The list of periodical comets is now very large, and increasingly 

 so. But many of this class of bodies still remain undetected, and 

 in proof of this Giacobini's discovery, in December last, of a comet 

 belonging to the Jovian family may be cited. 



Dennino's Comet (1894 I.). — The return of this object is expected 

 during the ensuing .summer, but under circumstances wliicli render 

 it probable that it will escape detection. Herr P. V. Neugebauer 

 gives the following sweeping ephenieris (Ast. Nach. 3700): — 



I, II. III. 



P.P. May 9. P.P. Miiy 25. P.P. Jiuie 10. 



a S a & a 6 



April 7 ... 60 6 + 21-7 539 + 19-4 48-4 + 167 



„ 23 ... 75-8 + 24-8 07-6 -t- 2:i7 6u 6 + 20-7 



May 9 ... 93 + 262 834 -I- 25-0 74 8 + 23-5 



„ 25 ... 111-2 + 25-6 1UU6 -I- 25-6 91-0 -t- 25-0 



June 10 ... 1290 -1-22 7 118-4 + 24-1 108-3 + 247 



„ 26 ... 145-3 + 18-2 135 6 -t- 206 1257 -I- 22 4 



At the return of this comet in 1894, 293 observations were made, 



and it was la.st seen on June 5th in the 30-inch refractor at Nice, 



when its distance from the earth was about 138 millions of miles. 



Fireball of January 13, 1901. — At lOh. 35m. a meteor 

 sufficiently bright to illuminate the sky was observed by the 

 Rev. S. J. .Johnson, of Bridport. Its course began mid-way between 

 a and 45 Cancri, and ended after a duration of 7 seconds right 

 across Castor. .\t first white, it finally dispersed in a stream of 

 rod sparks. The meteor was also seen at Beaniinster, Dorset, 

 wliere " its illumination resembled moonlight for about 10 seconds, 

 when it appeared to split into fragments and disappear in a brilliant 

 shower." It was also seen at Highbury, N., by ilr. Jewell, who 

 describes it as of exceptional size and brilliancy. The meteor was 

 ilircfted from a racUant at 149'' — ]2', and fell from 61 to 52 miles 



